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Syamsu  Suspended Member (Idle past 5619 days) Posts: 1914 From: amsterdam Joined: |
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Author | Topic: Clear faults in Darwin's formulation of Natural Selection | |||||||||||||||||||
Peter Member (Idle past 1508 days) Posts: 2161 From: Cambridgeshire, UK. Joined: |
I have a strong feeling of deja vu here but ...
quote: It depends on the scope and meaning of 'survival'. As you pointedout the style of Darwin's day was somewhat prosaic, and must be interpreted as 'lay' usage of language. One does not tend to refer to dying of old age as a failure to survive. Survival tends to refer to living past some unanticipatedlife-threatening event. In that, common usage, Darwin was completely correct. Many moreoffspring are produced than can possibly survive. Look at turtles, salmon, wild rabbits, and so on. Infant mortality rates in the wild are pretty high. Adult mortality rates are high enough! quote: The 'battle for existence', apart from being metaphorical, doesnot refer to battling one another to survive. It means that living a long and healthy life is not something thatcan be achieved in the wild without some considerable effort. quote: Tautology is a kind of literary redundancy, like saying 'baby puppy'. The above is a cause and effect relationship of sorts. IF A has an advantage over BTHEN A has a higher survival chance IF G has a higher survival chanceTHEN G is more likely to procreate quote: I'll try this again (although several months of posting have resultedin you starting from scratch again!!) 1. Animals are born2. Some animals die before reproducing 3. Some survivors procreate 4. Back to 1. 2. is natural selection.3. encompasses sexual selection. both 2&3 have some chance elements that get thrown into the mix. quote: No. quote: No. {Added by edit} The above NS sequence is not entirely accurate as there canbe a loop around 2-3. That is some animals may breed in one or two seasons, but be killed/die after that, while others may continue breeding into three or more seasons --> thus some parents leave more offspring than others over their lifespan (natural or cut-short). [This message has been edited by Peter, 02-13-2003]
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Peter Member (Idle past 1508 days) Posts: 2161 From: Cambridgeshire, UK. Joined: |
quote: So you disagree with the observations of naturaliststhe world over for many years? quote: Nonetheless, that's what the implication appeared to be. You, on the one hand, say that Darwin's writing is prosaic,and them on the other take each phrase as a formal description. The 'battle for existence' is a metaphor. quote: Yes. They must grow, spread out roots to gain nutrients fromthe environment in order to develop their seed-bearing mechanism of choice (flower, spore, what have you), they must bend their leaf surfaces toward the available light. There is a quite significant effort involved in a plant'sstruggle for survival. quote: The last part lost me ... but how exactly can the environmentextert an effort? quote: Why can effort only be where randomness is? Even if everything were predictable in advance, one would stillhave to expend energy to survive. quote: Only if you define 'advantage' as meaning 'higher chance ofreproductive success'. The usual formulation does not define advantage in that way. The usual formulation of NS says that those individuals withan advantage will have a higher chance of reproduction (see below for more). Advantage leads to greater reproductive success. quote: Think about what you just stated above. Organisms have a varying chance of reproduction. This means that some organisms can have a higher chance ofreproduction that others. A factors which will affect this include any trait which givesone organism a survival or breeding advantage over another organims (or group of organisms). quote: NS, as I have described it, applies to any organism (indeed toanything that self-replicates and interacts with an environment). If a plant has a seed with a better flight characteristic, andseeds stand a better chance of survival if they fall further from the parent, then the plant has an advantage. quote: 1. Whether or not a new-born/sprouted/etc. organism has any chanceof reproduction depends upon on it surviving to breeding age/maturity. 2. The number of offspring that any breeding-age organism leaves willincrease with each breeding season through which it survives. If an 'advantaged' individual bears 3/5 surviving young for 5 seasonswhile a 'dis-advantaged' individual bears 2/5 surviving young for 3 seasons there will be a shift in the overall population characteristic toward the advantaged trait(s). quote: If the 'definition' of NS you supplied in the previous post is 'your' definition then I have never agreed with this. I find it somewhat alarming that, after thinking we were movingtoward some common ground, you seem to have discarded all of the previous line of discussion and started back with 'NS don't work'!!
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Peter Member (Idle past 1508 days) Posts: 2161 From: Cambridgeshire, UK. Joined: |
You should appreciate the difference between a 'defintion'
and an 'illustration' or 'description'. Your original post here stated that Darwin's formulationof natural selection was in error. The three points you raised have been shown not to be errors. 1. 'Many more offspring than can possibly survive.' This is an observation of the natural world, not really opento dispute. Even with your board 'survival' concept this statement is true since none of the offspring will 'survive' in the sense that you use it. It the intended, and commonly understood usage of, 'survival'this statement is borne out by many examples; turtles, frogs, rabbits, ... pick an animal which still roams the wild. 2. 'Battle for existence' This, as you yourself pointed out, is prosaic. A metaphorfor the effort required to subsist in the wild. Do you deny that all creatures have to work with (and in some cases against) their environment to survive? Animals have to regulate their temperatures, and forage for food and water. Plants have to compete for water and other nutrients from the soil, and for sunlight from the skies, and (for flowering plants) to attract a sufficient number of pollinators. It is not easy in the wild habitats across the world. 3. 'Advantage' and 'greater chance of procreation' Are not the same thing. One has an effect on the other.Just because an individual is the biggest and the strongest deson't mean it WILL procreate more, only that it is more likely to on the basis of it's survival advantages. In terms of the glossary defintion here, there is no problem asfar as I can see with the way I describe NS, and the way the glossary defines it. Please point out where the views diverge. What is your actual objection to NS anyway? I have yet tounderstand this. If there is a drought, the individuals who can survive thedrought are the ones who get to procreate ... if they survived due to a heritable feature, then the future population will be better adapted to drought survival. It's not just about reproduction, which you even suggest in yourobjection to point 2 in your original post.
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Peter Member (Idle past 1508 days) Posts: 2161 From: Cambridgeshire, UK. Joined: |
I think you have missed the point entirely.
Survival means survival of unexpected events. Suppose a creature has an unimpeded lifespan of 25 years.Within that 25 years there are many instances when, due to some environmental factor, the organism could die. Due to some heritable trait, 20% of the population are moreliekly to reach the maximal, 25 year age than others. Also, 5% are, due to some heritable trait, only likely to reachan age of 6 years. The first group will leave more offspring than the lattergroup. The heritable trait frequency in the population will change. Survival does not mean immortal. Survival means the ability to survive adversity.
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Peter Member (Idle past 1508 days) Posts: 2161 From: Cambridgeshire, UK. Joined: |
1. The example I suggested in my previous post was as general
as I could make it. The organism in question could just as easily be a petunia bush as a fruit bat. 2. Survival in Darwin's sense doesn't mean what you are suggesting.All organisms have a natural maximum lifespan (they all die eventually), but not all individual organisms reach that maximal age. When one dies of old age, you do not hear (in English anyhow)people say 'Well they survived a long time.' they say 'He/she's had a good innings!' or 'They lived a long life.' 'Survive' does not mean 'live'. I can survive a fire or an earthquake or a drought (plants aresusceptible to those too you know that's why I chose it), but I don't 'survive' my life, I live it. Your problem seems to be the meaning that you ascribe to theword 'survival' ... your meaning is not the one commonly held amongst english speaking natives ... one of whom was Charles Darwin. All of that is off-the-topic here though. You stated3 'faults', I have explained why they are not faults. [This message has been edited by Peter, 02-21-2003]
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Peter Member (Idle past 1508 days) Posts: 2161 From: Cambridgeshire, UK. Joined: |
I have repsonded to the three 'faults' that you cited in your opening
post. You have then left them and carried on with a discussionthat we have been having for some months, but from a point somewhere back in time (months ago). The fundamental defintion of NS is not disputed anywhere. Some individuals have a survival advantage, and thereforetend to leave more offspring. If the advantage was a heritable one then there are moreindividuals in the population with this advantage than before. The above is how all evo's will understand NS. If you then wish to discuss how NS can drive evolutionyou will get some differences coming in as different people will have different ideas about how NS acts to promote evolution. They are two separate issues. NS happens. It is observed to happen. I really cannot seewhy you object so strongly to it.
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Peter Member (Idle past 1508 days) Posts: 2161 From: Cambridgeshire, UK. Joined: |
Variation is not essential to NS ... but without it
the net result is either a slide into extinction or rises in population numbers to levels supportable by the environment. The definition in the glossary does not require variation,it says that:: '[NS] often act[s] on hereditary (genetic) variation'{my emphasis} Often means that it doesn't always. The glossary defintionhere is one with which evo's will agree. If there is no variation then there is no evolution ... butthere is still natural selection. I still do not understand the exact nature of your objection tothe observed phenomenon of natural selection.
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Peter Member (Idle past 1508 days) Posts: 2161 From: Cambridgeshire, UK. Joined: |
First, I do not count variation as a requirement for NS.
You pointed that out correctly from your interpretation of my previous posts. Second, I made no comment on whether or not the studyof extinction was useful/interesting. I merely stated that the consequence of NS without variation in the population would be to either select against (leading ultimately to extinction) or selection for (leading ultimately to a population size only limited by available resources). In terms of thinking things through, I would have to contend thatit is you who are lacking. You have a view which you are no longer attempting to support in the slightest. Every time I suggest a NS description or respond to one of your posts in a negative manner you simply start stamping your foot and saying 'tisn't!' as far as I can see. What is you objection to Natural Selection?
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Peter Member (Idle past 1508 days) Posts: 2161 From: Cambridgeshire, UK. Joined: |
quote: Then we agree, and we can leave it at that. quote: I already pointed out in post #18 that the glossary defintionon this site does not state variation as a requirement for natural selection, but that when it acts on variation evolution results. The following links provide explanations or defintions forNS, none of them state that variation is a requirement. http://www.counterbalance.org/biogloss/natsel-body.htmlhttp://www.gate.net/~rwms/EvoDefinition.html#natural selection FishBase Glossary quote: I suspect you are misreading me, or that I have been unclear. Natural selection is not evolution. NS drives evolution, if and only if there is heritablevariation within a population. I think a part of the problem is that NS is not really consideredworth thinking about apart from in connection with evolution. The concepts are so fundamentally entwined that separating them becomes very difficult. Any illustrative description, or recorded observation of NS will focuss on cases where evolution has ocurred because that's when you see the 'power' of NS. No fundamental defintion of NS requires variation. Many defintions found are of 'evolution by natural selection'.
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Peter Member (Idle past 1508 days) Posts: 2161 From: Cambridgeshire, UK. Joined: |
1. The process by which individuals’ inherited needs and abilities are more or less closely matched to resources available in their environment, giving those with greater "fitness" a better chance of survival and reproduction.
Above, the part up to the italics is a definition of NS, thepart in italics is a consequence when variation is present. The definition does not require variation, it simply includes the consequence of natural selection. 2."Here are a list of the conditions Darwin thought were required for evolution by natural selection:......2. Organisms *vary* in many ways,..." This is under a list started by the phrase 'requirements forevolution by natural selection'. It is not part of the definition of natural selection. The last one I'll give you does include variation as part ofitsm defintion ... so maybe you are right that there is some disparity in views. On the otherhand the definition is targetted at evolution again. However, natural selection as described by Darwin IS theeffect of the environment on the individual. Variation is only required once we use NS to explain evolution. [This message has been edited by Peter, 02-27-2003]
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Peter Member (Idle past 1508 days) Posts: 2161 From: Cambridgeshire, UK. Joined: |
The main problem you are having is that you have
redefine natural selection for yourself. You seem to say:NS is whether or not a individual reproduces. Standard form is:NS is how environmental factors affect which individuals live to produce offspring (or more offspring). They are not the same. I do see that there are definitions stated as being of NS thatare so deeply entwined with 'evolution by ns' and that is not made clear. To re-iterate:: Evolution requires variation. Natural selection doesn't require variation. When considered as a mechanism for evolutionary changeconsidering NS without variation is not useful.
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Peter Member (Idle past 1508 days) Posts: 2161 From: Cambridgeshire, UK. Joined: |
Guilty as charged!! My wording was just as loose as those
definitions that you complain about. What I mean by NS (carefully worded this time)::Natural Selection concerns the environmental factors that affects the number of offspring produced by an individual. For NS the focus is not on competition, but on survival toreproduce. quote: And the above, in a nut-shell, is exactly how evolutionists viewit. If the photosynthesis trait arrived via a mutation, that meansthat the mutation introduced a new variant into the population. That variant could produce energy from sunlight, H2O and CO2, while other individuals could not. This gave it an advantage, and a greater chance of prolonged survival. Thus it left more offspring with the heritable ps trait than those that coud not do ps. Each of these generation-2 ps-plants also out-bred their non-ps peers, and so on. That is natural selection. Evolution requires variation. In your example, the mutationintroduced a variation. Not all individuals within the population suddenly develop the same mutation (unless you are Peter Borger). Natural selection is about the relationship between traits andsurvival (to reproduce).
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Peter Member (Idle past 1508 days) Posts: 2161 From: Cambridgeshire, UK. Joined: |
We have not been talking about evolution, we
have been talking about natural selection. No 'ancestral forms' are still around today. All life on earth (currently) has evolved over thelast 2-3 billion years (according to contemporary science). Two (or more) current organisms may have a common ancestor, but no living organism is ancestor to any other living organism (excepting its own offspring).
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Peter Member (Idle past 1508 days) Posts: 2161 From: Cambridgeshire, UK. Joined: |
It is highly unlikely that any creature exists today that
is completely unchanged from it's ancestors 2 billion years ago. When cells divide they suffer copy errors. Natural selection does not preclude two variants survivingwithin a population, or of the population splitting such that sub-population-A stays put and follows one evolutionary path, while sub-population-B moves on and follows another. The variation may even make the variants able to exploit different aspects of the same environment (I would suppose this to be possible). If you mis-understand natural selection as a concept, and it'sconsequences for evolution that does not mean that the concepts are wrong.
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Peter Member (Idle past 1508 days) Posts: 2161 From: Cambridgeshire, UK. Joined: |
Just because one variant is at an advantage doesn't
mean that the other variant will be wiped out. It may become less common, but not necessarily disappear entirely. Tell those who object to abiogenesis that highly unlikelydoes not mean impossible, please. Yes, I cannot say for certain, but logic says that since copy errorshappen, then over billions of years it would not be likely that any species would retain exactly the same genotype. There are some creatures which are phenotypically unchanged inany major, species defining feature ... but I don't think anyone is saying that they are identicle to their ancestors in the way that you seem to mean. A PS trait could evolve today, and maybe it did somewhere in theuniverse ... who knows, and what point were you making? You keep falling in back on this 'Darwin is wrong' thing, withoutbeing very clear as to why. Severla people here have described the most common understandingof natural selection to you. Whether you quible over how formal the definition is or not, NS happens and has been observed to happen. Organisms can only reproduce if they are alive. In a population there IS variation. Some variants will be able to stay alive longer than others. Those that stay alive longest will have the most opportunity forreproduction. Those that leave the most offspring will have the most impacton the genetic make-up (gene pool) of the future population. Where is the problem in that reasoning?
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